The present invention relates to a composition for hybrid seed production. More particularly the present invention also relates- to a composition useful for improving female fertility and seed setting in plants. The composition of the present invention is useful for production of hybrid seed in crop plants such as wheat.
Capability of certain classes of chemicals viz. pyridazines, 4-pyridionones, pyrrole carboxylates, 5-chlorocaboxylic acids to effect such changes is know in the literature. Certain compounds designated as DPX 3778, Hybrex, LY 195259, Mendok, RH 2956, RH 4667, RH 5148 and WL 84811 are few of the examples of such compounds. (Pickett A A 1993. In xe2x80x98Advances in plant Breedingxe2x80x99 15, Paul Parey Scientific Publisher, Berlin, pp 122-132). However, these chemicals also affect female sterility resulting in lower seed setting and seed germination.
The prior art compositions/compounds suffer from several disadvantages in use such as resulting in some growth inhibition, severe plant damage, small seeds, inhibition of growth and flowering, leaf burn, shorter plant, etc. In view of the above limitations it is necessary to provide chemicals and their combinations, which may provide foolproof male sterility with better female fertility for commercial seed production of hybrid seed. Although the study and the research was carried out on wheat in the present description, the involved compositions are not only applicable to the wheat plant but are also to other angiosperm crops as rice, maize, jowar, bajra, etc.
Based on the mode of pollination, the crop plants are classified into three broad groups namely, self-pollinated, cross pollinated and often cross pollinated. Exploitation of heterosis through hybrid breeding is common in cross pollinated and often cross pollinated as their floral structure facilitate natural out crossing. Wheat is a self-pollinated cleistogamy flower wherein flower open only after anther had released their pollen load inside the floret. The success of hybrid breeding depends upon how economically hybrid seed can be produced specially in self-pollinated crops. The three plant breeding methodologies known to develop hybrids are genetic, cytoplasmic and cytoplasmic-genetic. The success story of hybrid rice is a suitable example for a cytoplasmic male sterility (CMS) System.
During the process of evolution the A, B and D genomes of Triticum spp and other related species had combined to form the present hexaploid wheat that man effectively domesticated and commercially grew for food as a cereal crop. These genomes have an ability to survive independently in nature. This hexaploid nature of wheat could be a probable reason that restricts the use of CMS system of hybrid seed production. The initiation of global efforts to use CMS system in early fifties using different sources of male sterility as a mode of hybrid wheat seed production, faced three main limitations viz. A. Instant ability of male sterile line over years; B. Lack of complete restoration; C. Limited use of parental lines because of the tedious and time consuming procedure to develop. A line (male sterile line); B line (maintainer) and identifying good R line (restorer).
Due to these difficulties, several organizations in the early 1970""s shifted their efforts to the use of chemicals, which can act like gametocides or pollen suppressant. These chemicals were referred to as xe2x80x9cChemical Hybridizing Agentxe2x80x9d (CHA) and a number of CHAs were evaluated. In last 15 years progress has been made for commercial exploitation of hybrid wheat through the use of CHAs (see table 1). Table 1 given below shows the results of investigations made using various chemicals as chemical hybridizing agents (CHA""s).
Since early eighties a number of CHA molecules were evaluated against wheat (see Table 1) that had variable effect on male and female sterility and some of them affected the plant morphology and caused seed shriveling.
These chemicals differ with respect of female fertility, duration and dose specificity, genotypic and tissue specificity, developmental stage, physiological state, chronic spray, fertility impairment, detrimental side effect and phyto-toxicity. (Mahajan V, Nagarajan S 1997. PINSA B64 No. 1 pp 51-58).
In spite of these difficulties a suitable CHA may have a public acceptance if it is an easy, economical and reliable method for inducing selective male sterility over diverse environments. The CHA can also become an effective tool for emasculation in a traditional breeding programme.
In 1997-98, both Ch 9701 and Ch9832 were evaluated over different genotypes (Mahajan V, Nagarajan S, Deshpande V H and Kelkar R G 2000. Current Science 78 (3): 235-237). At a minimum effective dose for complete male sterility, the female sterility and seed shriveling was higher in CH9701 while seed setting was numerically higher in CH9832. The seed germination was comparable (Table 2).
Thus all previous research on CHA was not successful in identifying a combination of chemicals which may provide a functional hybrid seed production method in wheat with higher female fertility, seed setting, seed yields, seed viability and versatility over a range of genotypes and environments.
The main object of the present invention is to provide a novel composition for hybrid seed production.
Another object of the present invention is to provide a composition to improve female fertility.
Still another object of the present invention is to provide a composition useful for increasing seed setting.
Yet another object of the present invention is its effectiveness over a range of genotypes and environments.
Accordingly the present invention provides a composition for hybrid seed production, which comprises a synergistic mixture of potassium 1-[4-chlorophenyl]-1,4 dihydro-6-methyl-4-oxopyridazine-3-carboxylate of the formula 1
and potassium 1-[4-fluoro, 3-chlorophenyl]-1,4 dihydro6-methyl-4-oxopyridazine-3-carboxylate of the formula 2
In one embodiment of the present invention, the compounds of the formula 1 and 2 are taken in a combined dose of up to 1000 ppm along with a non-ionic surfacant.
In one embodiment of the invention the concentration of potassium 1-[4-chlorophenyl]-1,4 dihydro-6-methyl-4-oxopyridazine-3-carboxylate is in the range of from 1 ppm to 300ppm.
In another embodiment of the invention, the concentration of potassium 1-[4-fluoro-3-chlorophenyl]-1,4 dihydro-6-methyl-4-oxopyridazine-3-carboxylate is in the range of 700 ppm to 999 ppm.
In still another embodiment of the invention, the non-ionic surfactant is selected from the group consisting of polyoxyethylene sorbitan monoaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monooleate, polyoxyethylene sorbitan trioleate and any combination thereof.
In yet another embodiment of the invention, the concentration of the non-ionic surfactant is in the range of 1-10% of an aqueous solution prepared from a mixture of compounds of formula 1 and 2.
The present invention also relates to a process for the preparation of a composition for hybrid seed production, comprising a synergistic mixture of potassium 1-[4-chlorophenyl]-1,4 dihydro-6-methyl-4-oxopyridazine-3-carboxylate of the formula 1
and potassium 1-[4-fluoro, 3-chlorophenyl]-1,4 dihydro-6-methyl-4-oxopyridazine-3-carboxylate of the formula 2
said process comprising mixing said compounds of formula 1 and 2 in a non-ionic surfactant such that the combined dosage of the compounds of formula 1 and 2 is up to 1000 ppm.
In one embodiment of the invention the concentration of potassium 1-[4-chlorophenyl]-1,4 dihydro-6-methyl-4-oxopyridazine-3-carboxylate is in the range of from 1 ppm to 300ppm.
In another embodiment of the invention, the concentration of potassium l-[4-fluoro-3-chlorophenyl]-1,4 dihydro-6-methyl-4-oxopyridazine-3-carboxylate is in the range of 700 ppm to 999 ppm.
In still another embodiment of the invention, the non-ionic surfactant is selected from the group consisting of polyoxyethylene sorbitan monoaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monooleate, polyoxyethylene sorbitan trioleate and any combination thereof.
In yet another embodiment of the invention, the concentration of the non-ionic surfactant is in the range of 1-10% of an aqueous solution prepared from a mixture of compounds of formula 1 and 2.
The present invention also relates to the use of a composition comprising a mixture of compounds of formula 1 and 2 above in an non-ionic surfactant for hybrid seed production.
The composition of the invention enhances functional male sterility with improved female fertility facilitating commercial production of hybrid seed of wheat and other crops, cereals in particular, across a range of environments.